Very nice little lens, capable of quality images. I usually use with a rubber washer in the adapter to give a f4.5 aperture, although it is also nice wide open. Use a hood. Gives images a different 'look' than modern optics:

Bought this lens out of curiosity, I've been using it on my NEX 5n with an m43 adapter with aperture lever and a m43 to NEX adapter. Having the lever is really useful.
I love it's unique color rendering and it's distorted bokeh, it really is great for portraits. I use it from time to time.
Now I even use it on my Sony A7 (!!) which is usually a weird combination but brings amazing results! Following samples were taken with NEX 5n though

Many of my favorite Auto 110 Pentax pictures are posted at JustNex.com. I have 14 digital cameras and many lenses, and the combination of NEX-5 and 18mm Pentax 110 is a great package. It makes for a light camera. I shoot it at the fixed f2.8 usually 1/4000 on a sunny day. It is a good close up lens.

On film I will point out.
Kodak or Fuji. The lens has delivered very good images. Recently I've purchased the Lomography 110 b&w film and it is very good. So far is that this lens does will to put image to emulsion and the flare and contrast quality is very big lens in performance. No surprises in any way and I'll let you know if I cut Ektar down to 16mm how it all works out.

Picked up this lens to use on the Pentax Q with an adapter, since the Pentax-110 24mm was not a good companion.

It is a very interesting lens in use, for pixel level sharpness I would say it is very good, however many images exhibit a certain dreamy softness which is very appealing when using this as a portrait lens (100mm equivalent on Q). I find this "dreamy" look happens most often in side-lit situations, so it is simply a veiling flare, but I've never seen veiling flare look this nice.
If you're not into the dreamy veiling flare: fashion a lens hood out of something, and this would be a very competent lens in any lighting.

Here's one shot demonstrating sharpness, another the nice out-of-focus highlights this lens delivers. In the future I'll add a shot of two demonstrating the dreamy qualities.

A very nice, small lens with great sharpness and, what's more important, giving a nice vintage look to pictures made with my Nex-5N (strong vignetting may be one of the reasons...). Of course one cannot change the aperture, but it doesn't have to be a bad thing, as it makes you think before taking a picture. And for objects located a bit further the DOF is deep enough.
Nice distortion control for such a small and old lens, bokeh is acceptable (good for a wide lens), it's sharp wide open and very nice to handle.
I bought it in a set of a camera, flash and two other lenses (24mm f/2.8 and 50mm f/2.8) for ca. 60 USD and don;t regret a penny spent! :-)

Practically this lens is about equivalent to 28mm/35mm film on Sony NEX-5.
Compare with Sony SEL1855 this lens shows cleaner image in the room light. Because Sony Zoom can go f/4.0 max, but it goes f/2.8.
It is such a small lens that one can not resist to carry it.